Human studies suggest that acquired immune responses modify congenital cytomegalovirus (CMV)-induced disease. In these studies we will explore the roles of maternal, fetal, and neonatal immune responses to the pathogenesis of congenital CMV infection, employing the well-defined guinea pig CMV model which simulates human congenital infection. We will first perform detailed longitudinal in vitro studies of cell-mediated immune capabilities in each trimester and postpartum using blood and spleen cells obtained during normal uninfected guinea pig pregnancy. We will investigate proliferative responses to mitogens and to alloantigens, the later being major histocompatibility complex (MHC) Class II restricted. We will also study cytotoxic responses in uninfected pregnant animals and their fetuses/neonates as to endogenous MHC-unrestricted natural killer (NK) cell and antibody-dependent cell-mediated cytotoxicity (ADCC). Having defined the immune capabilities in uninfected pregnancy, we will then define perturbations and acquisition of immune responses in pregnant animals and their fetuses during infection with guinea pig CMV in each trimester. Confirmation of the extent of infection will be carried out by use of both viral culture and DNA hybridization techniques. Cell-mediated immune parameters to be investigated include proliferative responses to mitogens, alloantigen and CMV antigen, and cytotoxic responses (NK, ADCC, and MHC class I restricted cytotoxic T-lymphocyte assays). Since antibody may modify CMV disease expression, we will also examine humoral immune responses by plaque neutralization, by class (IgG, IgA, and IgM) using ELISA, and to specific CMV antigens by immunoblot technique. Comparisons of immune responses to infection acquired during each trimester will be correlated with rates and extent of transplacental infection and the outcome of pregnancy. Using the same techniques and immune assays, we will also compare immune responses and rates of transplacental infection during pregnancies that occur after recovery from virulent salivary derived guinea pig CMV infection to those of pregnancies after recovery from attenuated multiple tissue passaged guinea pig CMV.